The present invention relates to surface finishing tools, such as are used for sanding, buffing, and polishing, and more particularly, a rotary surface finishing tool of a relatively simple construction and a method of making such a tool.
Rotary surface finishing tools, used to provide a wide variety of surface finishing functions including sanding, buffing and polishing, are well known in the art. As used herein, the term xe2x80x9crotaryxe2x80x9d is meant to include orbitally driven finishing tools which, in most delicate finishing operations, are preferred because of the reduction in swirl marks in the finish of the workpiece. Rotary finishing tools are typically circular in shape and are mounted on the drive spindle or arbor of a powered rotary or orbital driver which is held and manipulated by an operator.
The finishing medium used on rotary finishing tools includes wool and/or other synthetic fiber yarns that are tufted to a fabric backing layer, such as jute, and which are permanently or demountably attached to some sort of backing plate device, the backing plate being attached to the drive spindle of the powered rotary driver. Polymeric foam material is also used as a finishing medium. Such foam materials may be in the form of a solid circular block adhesively attached to a backing layer or an array of polymer foam fingers individually attached to a backing layer in a modified tufting or stuffing operation. The backing layers of either of these types of pads may also be further modified to provide permanent or demountable connection to a rotary backing plate. Demountable connection of a finishing pad to the rotary backing plate is often accomplished with the use of a hook and loop fastening system (i.e. Velcro). However, it is well known that such hook and loop fasteners often deteriorate under the vibration of high speed rotation and fail prematurely. It is also known to utilize flexible polyester or other plastic layers to form laminated backing layers in lieu of woven jute or similar natural fibers.
All of the foregoing surface finishing pads require multiple steps or operations in their fabrication. A more simple and less labor intensive finishing pad construction would be desirable because the pads are eventually worn to the point where they must be discarded. Utilization of less costly materials in fabrication of the pad would also be desirable.
In accordance with the present invention, a rotary surface finishing tool, preferably utilizing a polymer foam finishing medium, comprises a simple three-piece construction that may be assembled in a two-piece die utilizing a simple crimping technique. The three-piece assembly includes the foam body, a cup-shaped backing plate, and a locking ring.
In accordance with the preferred method of making the finishing tool, a relatively rigid circular backing plate is placed to engage the foam body opposite the finishing face. The backing plate may comprise a stamped steel shell, but other malleable materials, such as aluminum, may also be used. The flexible outer peripheral edge of the foam body is deformed around the outer edge of the backing plate and is captured by a locking ring having a diameter less than the diameter of the backing plate. The outer edge of the backing plate is then crimped over the outer edge of the locking ring to secure the edge of the foam body therebetween. Preferably, the outer peripheral edge of the backing plate is preformed to a cup-like shape, and the steps of capturing the foam and crimping the edge of the backing plate over the edge of the ring comprises pressing the foam body, backing plate and locking ring together in a die.
In accordance with one embodiment of the method, the locking ring is provided with an integral rotary drive hub. In accordance with an alternate embodiment, the backing plate is provided with an integral rotary drive hub.
A rotary surface finishing tool of the present invention comprises a generally circular body of a finishing material that includes a flexible peripheral edge, a front finishing face and a rear mounting face. A rigid cup-shaped backing plate engages the mounting face of the finishing material body and the flexible peripheral edge of the material body is wrapped around the cupped outer edge of the backing plate. A locking ring having a circular peripheral edge is pressed against the flexible edge of the material body and into the cup-shaped backing plate. The cupped outer edge of the backing plate is crimped around the peripheral edge of the locking ring to secure the flexible peripheral edge of the finishing material therebetween.
In a preferred embodiment, the finishing material comprises a polymeric foam. In another embodiment, the finishing material comprises a fabric-backed tufted wool or other yarn. The cup-shaped outer edge of the backing plate is formed of a malleable metal, preferably steel or aluminum. A central drive hub is provided which may be alternately formed as part of the locking ring or the backing plate.